90

GELATIN—EAT.

wet, it is very liable to change: when heated, it bums ;and the results of its decay, as well as its combustion,are, water, carbonic acid, and ammonia.

275. The muscle or flesh of animals consists princi-pally of fibrin, associated with albumen and gelatin;fibrin is insoluble in hot or cold water ; when dry, itmay be easily preserved ; but when moist, like albumenand gelatin, it soon begins to decompose. The compo-sition of fibrin is identical with that of albumen; theyconsist of the same elements, united together in the sameproportions.

276. Gelatin , the third great principle of animalmatter, is a tough, colourless substance ; in cold water,it very slowly softens and dissolves ; in boiling water,it dissolves more readily, and forms a solution whichbecomes a jelly as it cools. The skin, horns, and hoofsof animals consist principally of hard, dry gelatin ; andit likewise occurs in many of the softer parts of thebody, associated with albumen. Common glue andisinglass consist almost wholly of gelatin; the formeris prepared by boiling the clippings of skin, refusehorns, hoofs, and similar matters, in water; a strongsolution of gelatin is thus obtained, which, as it cools,becomes a jelly; this jelly, cut into slices and dried, isthe glue of the shops.

277. The fat of animals is perfectly similar in natureto vegetable oil; some kinds of fat are solid, othersfluid, at common temperature ; but they are all fluidwhen made sufficiently hot ; animal oils, like those of